Combustion performance in a cylinder may be affected by many factors, including spark timing and compression ratio. To increase the power output of the engine, aggressive spark timing and high compression ratios may be used. However, the aggressive spark timing and the high compression ratios may drastically increase the temperature of the cylinder. The elevated temperatures may lead to increased emissions from the engine and in particular increased generation of nitrogen oxides (e.g., NOx). Knocking may also occur when the cylinder is at an elevated temperature. Moreover, thermal degradation (e.g., warping) of the engine components may occur due to the elevated temperatures. Therefore, the spark timing and compression ratio may be limited by the temperature of the combustion chamber, such as during peak loads.
US 2006/0207543 discloses an engine lubrication system which includes a spraying nozzle for directing engine oil toward the underside of the pistons. The oil spray may reduce the temperature of the piston and therefore the combustion chamber. The lubrication system discloses in US 2006/0207543 also includes an oil cooler for removing heat from the oil.
However, the Inventors herein have recognized that only a portion of the engine oil may be used to cool the pistons and the remainder may be used for component lubrication. It may be undesirable to cool oil used to lubricate components. For example, decreasing the temperature of the oil used for lubrication may increase oil viscosity above a desired valve, thereby increasing friction losses in the engine. Therefore, cooling all of the oil circulating in the lubrication system may increase fuel usage, as well as engine wear. Furthermore, during peak loads, oil coolers using engine coolant may not provide a desirable amount of cooling to the oil sprayed onto the pistons, due to the elevated temperature of the coolant. For example, oil coolers using engine coolant may not be able to decrease the temperature of the oil under a threshold temperature (e.g., 220° F. in some engines) needed to reduce thermal degradation in the combustion chamber.
As such in one approach, a system in an engine is provided. The system may include a piston spraying conduit including an inlet in fluidic communication with an oil reservoir, a nozzle in fluidic communication with the piston spraying conduit, the nozzle directing an oil spray toward an exterior surface of a piston positioned within a combustion chamber, and a heat pipe transferring heat from an evaporator section to a condenser section, the evaporator section coupled to the piston spraying conduit.
In this way, heat may be strategically removed from the engine oil directed at the piston. As a result, cooling may be provided to a desired portion of the engine oil without cooling the engine oil used to lubricate engine components, if desired. For instance, a heat exchanger may not be included in an engine lubrication system in the engine, in some embodiments. Moreover, the heat pipe enables heat to be passively removed from the oil without the use of a controller, if desired. Additionally, providing cooling to the piston via the heat pipe lowers the temperature of the combustion chamber, enabling higher compression ratios and more aggressive spark timing strategies. As a result, the power output of the engine is increased.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.